1. Field of the Invention
The present invention relates to an internal combustion engine and a vehicle including the same. More particularly, the present invention relates to an internal combustion engine used in a riding type vehicle (for example, motorcycle) which prevents kickback from occurring.
2. Description of the Related Art
In a motorcycle, a phenomenon referred to as “kickback” (refer to, for example, JP-A-60-187766 and JP-A-2002-221138) occurs. As described in JP-A-60-187766 and JP-A-2002-221138, “kickback” is a phenomenon in which when starting an engine (internal combustion engine), ignition by an ignition plug occurs immediately before an upper dead center of a piston, the piston is pushed back before reaching the upper dead center by an explosion force thereof, and the engine is caused to rotate reversely and to abruptly stop.
According to JP-A-60-187766, in order to prevent kickback, an engine starting apparatus is described which prohibits operation of an ignition apparatus until an engine reaches a predetermined rotational speed. Furthermore, in JP-A-2002-221138, an engine starting apparatus suitable for a motorcycle is disclosed which includes an engine automatic stopping and starting apparatus which is stopped in response to a predetermined stopping condition when a vehicle is running and restarted in response to a predetermined starting operation after being stopped.
When kickback occurs, a large reverse rotating torque is produced in a power transmission system between a crankshaft and a starter motor. In order to prevent a component of a starter system (for example, one way clutch, starter motor or the like) from being damaged by the reverse rotating torque, a torque limiter or other suitable device is used as a countermeasure. However, such a countermeasure increases the cost and/or weight, which is a problem, particularly in a motorcycle.
Although starting apparatuses capable of preventing kickback are disclosed in JP-A-60-187766 and JP-A-2002-221138, it is known that kickback occurs at times other than during starting, and it is preferable to provide a countermeasure against kickback so as to securely prevent kickback at times other than during starting. Further, although in JP-A-60-187766 and JP-A-2002-221138, when kickback is anticipated to occur, kickback is prevented by stopping the ignition. However, stopping the ignition produces an unnatural, strange feeling to a rider.